The implantation of an intraocular lens for restoring vision after cataract surgery is well-known in the art. In general, two forms of surgery are used to remove cataracts. These are extracapsular cataract extraction and intracapsular extraction. (Discussed in U.S. Pat. Re. No. 31,626 to Hoffer). Following extraction of a cataractous lens, an intraocular lens is normally implanted in either the anterior or the posterior chamber of the eye. In an anterior chamber implant, the lens is generally situated forward of, or mounted to the iris. In the case of posterior chamber implants, the lens is situated behind the iris and may be mounted within the cleft or fornix of the capsule which remains in place after extracapsular surgery.
In both anterior or posterior chamber implants, the lens is usually centered and fixed in position by one or more supporting strands or haptic members. While available intraocular lenses incorporate haptic member(s) having various geometric shapes and configurations, the typical haptic member is a flexible strand of non-biodegradable material which is fixed to the lens body, and exhibits specific spring-like memory qualities so that the haptic member can be compressed or off set from the normal rest position and thereafter returned to the fully extended condition when pressure is removed. (See U.S. Pat. Nos. 4,468,820 to Uhler et al.; 4,435,855 to Pannu; and 4,494,254 to Lopez.)
The typical diameter or thickness of a haptic member is about 0.1-0.2 mm; and therefore requires careful handling prior to and during implantation of the lens. For example, a haptic member can break or weaken when improperly handled with a surgical instrument, such as forceps. A broken haptic renders the lens useless. In the case of an integral one-piece lens a broken haptic requires that an entirely new lens be used.
While not common, it is possible that improper handling of a haptic prior to lens implantation may damage the haptic without breaking it. If a lens with a damaged haptic is implanted and the haptic breaks subsequent to surgery, serious complications can arise. Dislocation of a lens subsequent to surgery could seriously impair vision and/or damage the eye.
Among the wide variety of intraocular lenses having haptic support members, all known haptics have a uniform cross sectional dimension or thickness. When pressure is applied to the haptic (i.e. grasping root or base area of haptic with forceps) stress is concentrated at a relatively small area, thereby increasing the potential for breakage in the area of concentrated stress.
It is well known that distortion of the eyeball can be caused by normal physical activities such as walking or rubbing the eyelids, as well as by more severe physical contact such as falls or collisions. When an intraocular lens has been implanted, distortion of the eyeball can place intermittent stress on the haptic members. This intermittent stress generally results in eye irritation, redness or other minor trauma. It is believed that these intermittent stresses can be minimized by increasing the flexibility of the haptic members. However, if haptics of the type currently available are made thinner to increase flexibility, the potential for breakage is also increased.
Accordingly, a substantial need exists for a haptic support member which exhibits high resistance to breakage when handled. The present invention provides an artificial lens having an improved haptic member which is strengthened to minimize breakage. The strengthened haptic member of the present invention also provides for thinner more flexible haptics without sacrificing needed strength.